GENEVA (Reuters) - Geneva's main hospital appeared to burst into flames on Monday night in a simulation to commemorate the deadly U.S. air strike on a Kunduz hospital in Afghanistan a year ago and to condemn Syrian and Russian bombing of health centers in Aleppo.

The event was organized by Medecins Sans Frontieres (Doctors Without Borders), which ran the Kunduz trauma center destroyed in the one-hour bombing on Oct. 3, 2015.

Forty-two people, including 14 of the medical charity's staff, were killed in a U.S. strike that the Pentagon later said did not amount to a war crime, blaming human error and equipment failure.

Four hospitals in rebel-held Aleppo have been destroyed during the Syrian-Russian air campaign in the past week, leaving just five intensive care beds for 250,000 people, the group said.

"We are gathered to express our sadness and consternation but also our indignation," Joanne Liu, president of MSF International, told the crowd gathered outside Geneva University Hospital.

"But these attacks haven't stopped with Kunduz. Over the last 12 months, the extent of the destruction of hospitals and clinics in Yemen and Syria leaves us speechless ... Aleppo is on fire, it is a bloodbath."

World Health Organization spokeswoman Fadela Chaib said that many of the 250,000 people trapped in rebel-held eastern Aleppo lacked health services after repeated bombings of hospitals.

"We have now only six partially functional hospitals that are in service, only one hospital offers trauma care services," she told a briefing.

The Geneva hospital, where U.S. Secretary of State John Kerry was treated for a broken femur in May 2015, was lit up on Monday night with projections of war planes bombing it. Images of patients, doctors and nurses scrambled behind the seemingly shattered windows as the wards appeared to burst into flames.

Dr. Kathleen Thomas, an Australian doctor who survived the U.S. gunship attack on the 92-bed Kunduz hospital serving nearly one million people in northern Afghanistan, testified to the horror.

"We scurried around the room like rats in a cage," she said. "Patients were burning in their beds."

North-eastern Afghanistan has been left without a trauma center, Thomas said. "This is not just a mistake occurring in the fog of war. This is a tactic of war."

Thomas Nierle, president of MSF Switzerland, said another ceremony planned in Kunduz had been postponed on Monday as Taliban fighters fought their way into the provincial capital.

"Without an independent investigation we will never know what happened," Nierle said of the U.S. attack.

In the past year, MSF health centers have been attacked 80 times, mainly in Syria and Yemen. "It has become part of the military and political strategy," he told Reuters.

Using the hashtag #NotATarget, MSF is trying to raise the profile of cases where civilians, humanitarian workers and hospitals are hit in war zones.